Hovering aeroplane



A. F. ZAHM.

HOVERING AEROPLANE. APPLICATION FILED AUG.10, 1917.

1,358,603, I Patented Nov. 9, 1920.

n 12 I l7 21 .20

AQBERT F.'Z.AHM.

ALBERT r. ZAHM, or wasnrne'ron, ms'rrarcr or COLUMBIA.

Hovnnme AEROPLANE.

Specification of Letters Patent.

Patented Nov. 9,1920.

Application filed August 10, 1917. Serial No. 185,488.

To all whom it may concern Be it known that I, ALBERT F. ZAHM, a citizen of the United States, residing at Washington, in the District of Columbia,

have invented certain new and useful Improvements in Hovering Aeroplanes, of which the following is a specification.

My invention relates to airplanes. ft is capable of horizontal flight, volplaning' and climbing, and under such conditions is supported wholly by air reaction upon one or more supporting surfaces of aerofoil form. It is further capable of vertical or nearly vertical flight and of hovering suspended, as it were, immovable in mid air. In starting it may be launched into the air without any or any substantial preliminary run, and if desired may alight under similar conditions. Briefly it may be described as of a construction such that the various charac teristics of the conventional aeroplane are retained with the added characteristimof a helicopter.

A characteristic of the invention is the landing gear construction. The landing gear is preferably carried back from a point in advance of the transverse vertical plane of the center of gravity and curved upwardly and rearwardly whereby the machine can be rocked or tilted back sufficient to elevate its forward end. When thus positioned the machine can be started and the usual long preliminary run completely or almost completely eliminated.

In gaining vertical lift, with the nose end of the machine elevated, it is proposed to use a very light motor or motors in which the weight is reduced to two lbs. or less per h. p.; it being well known that a 300 11. p. motor of this type with a propeller properly designed will give an axial thrust of between 1500 and 2000 lbs. and weigh approximately 600 lbs. Preferably a multiple number of tractor propellers are used. These propellers are disposed in such relation to the sustaining surfaces that the propeller slip stream acts upon practically the full surface area as well as upon the controlling surfaces usually mounted at the wing tips and at the tail end of they machine. Through this arrangement of all. control surfaces in the propeller slip stream all controls are made effective whether traveling vertically, horizontal-ly or at an angle or while hovering in the air. When traveling vertically sufficient vertical lift is realized from the propellers revolving in a horizontal or approximately horizontal plane to lift the machine bodily in a vertical line oi at a slight inclination to the vertical. In attaining this result the high speed now attained in horizontal travel will in all probability be lessened somewhat owing. tothe fact that the propeller pitch will probably be lowered a considerable degree below the usual value.

The advantages of a machine of this type are that it can be launched vertically (for instance from the deck of a vessel) by merely tilting the nose of the machine upward; it can fly horizontally supported entirely by air reaction upon the aeroplane wings; it can be balanced regardless of the direction of flight by the conventional form of conflecting the ailerons downwardly and simultaneously increasing the angle of incidence of the planes so that the air blast from the propellers reacts upon the planes; and it can be made to literally climb straight up without tilting the nose end of the machine upward through nullification of the thrust value in any suitable manner without a corresponding nullification of the lift value obtained through the reaction of air upon the wings. (This latter operation may be effected in a number of different ways; such for instance as holding the machine captive until it has risen into "the air and then releasing it, or erecting standards at opposite sides of the fuselage and equipping the fuselage with lugs which extend out laterally so as to engage the standards at the rear). Other advantages will be hereinafter pointed out.

Of the drawings:

Figure 1 is a side elevation of a multiplane hovering machine having the characteristics of tlie invention claimed;

Fig. 2 is a front end elevation of the machine illustrated in Fig. 1; and

Fig. 3 is a side elevation of a modified type of machine having the same characteristics as the machine illustrated in said Figs. 1 and 2. p a Tn Fig. 1 the body of fuselage of the machine is designated in its entirety by the numeral 10. lit is equipped with a multiple number of superposed supporting surfaces 11, preferably, three. These supporting surfaces are in-turn equipped with intercon nected ailerons 12B of relatively large area.

The power plant comprises three motor units located respectively at the nose end of the fuselage and intermediate the supporting surfaces symmetrically out from the median fore and aft axis of the craft. Said motor units have been designated respectively 13, 14: and 15. The supports'for the till dll

motor units 13 and 15 may be of any well known construction; preferably of sturdy type lrnown in the art as the vee.

Each motor unit is equipped with a tractor screw or propeller of a determined pitch and size. The pitch of the propellers is such that sufficient vertical lift is realized from the propellers when revolving in a horizontal plane to bodily lift the machine.

on a vertical line (or at a slight inclination) into the air. The size of the propellers is such that the slip stream which flows back from the propellers is distributed substantially uniformly over approximately the entire supporting surface area and in such relation to the control surfaces that all said surfaces are efl'ective whether the machine be travelin vertically, horizontally or at an angle. aid propellers have been designated respectively 16, 17 and 18.

-At the tail end of. he fuselage (which in the embodiment of the'invention is the forward end) the usual rear controls are (lit tillprovided. aid controls include a vertical rudder 19, elevator flaps 20, vertical staoperation of the craft as a helicopter would be impossible, With the weight of the motor units thus reduced and the pitch of the pro-- pellers designed as indicated sufficient ver-.

tical lift can be realized to lift the machine bod1ly up in the air. Flight may be started intense pyramidal to a maximum degree.

I under such conditions by simply tilting the nose end of the machine upwardly Canard style, in which event, although the climb or vertical lift be relatively slow, both directional control. and lateral balance are effected through the usual manipulation of the various controls. a

llf vertical lift is desired in starting without changing the flying attitude of the ma- I chine, c'. c. with the longitudinal axis of the fuselage extending horizontally; this may. be done by nullifying the thrust value until sufficient lift is obtained through the reaction of the propeller slip stream upon the.

aeroplane wings to bodily lift the machine into the air. Anysuitable means may be provided for obtaining this nullifying effect; Furthermore, when flown as a hellcopter, a hovering action is obtainable by simply throttling the motors to such an extent that'the lift value of the propellers equalizes the action of grav ty.

llf desired a'single motor unit may be substituted for the three disclosed. Tf the machine is thus equipped the single motor unit should be located inside the fuselage and connected up with driving shafts which extend out right and left from the motor for suitable driving connection with propellers located respectively at opposlte 'sldes of the motor. In effect this arrangement 18 equivalent of the multiple power plant arrangement herein illustrated. The total weight of the craft however may in this wa be reduced.

referably all parts of the machine are streamlined, and where possible, lightened In actual flight a machine constructed as herein set forth may fly alternately as a heavier-than-airfiymg machine and helicopter, With the motors developing maximum power stalling in mid air is impossible, for as the machine is swung into an acute angle to the vertical the thrust value of the propellers is such that a direct vertical climb rather than a falling back, as heretofore, results.

As intimated, in a Canard type machine the tail unit is forwardly located. Herein T have illustrated directional control sur-.

Mill

llltl faces placed both forwardly of and aft of r will of this type in the manner stated maybe f= readily accomplished because of the fact that its center .of gravity is well toward the rear and itmay therefore be provided effort would be requiredt'o nose the machine with a launching and landing skid of a construction enabling the machine to be rocked back without undue effort. The skid arrangement illustrated extends from a point well forward to a point well to the rear of the transverse vertical plane of the center of gravity. curved upwardly and rearwardly,thecenter machine. By constructing the skids .in the manner stated little effort is required to tilt it back until its nose end points substantially vertically. Of course the skid, or rather its longitudinal curvature need not be described from a point coincident with the center of gravity although it is preferred that the skid be so constructed. Moreover, a skid of the type mentioned is not necessarily limited in its applicationto machines of the Canard type. tional airplane may be provided with a skid of this character although in all probability the machine could not be tilted upwardly to the same extent. In launching the machine illustrated in Figs. 7 and 8 the entire machine is rocked back until its nose endpoints vertically or nearly so. Being thus positioned it would readily take to the air without any preliminary run whatsoever. If the nose end be elevated to a lesser degree the preliminary run, while not completely eliminated would be minimized due to the fact that after a very short run the machine would rise in the air.

The landing gear per 86 comprises a skid 44 which extends from a oint in advance of the transverse vertical p ane of the center of gravity rearwardly to a point consider ably aft thereof. Its curvature ahead of the transverse vertical plane of the center of gravity is immaterial, although preferably .of a curvature similar to that illustrated. Its curvature aft of the center of gravity however is of considerable importance in that by describing the arcuate line of the skid 44 about a center coincident to the center of gravity the ease of rocking or tilting action is enhanced. If the curved extensions of the skids be too far removed back of the center of gravity a considerable up as its launching without a preliminary run requires.

As in the conventional t pe of machine the control surfaces of the danard machine are all in the propeller slip stream. In Fig. 3, wherein a somewhat different character of machine is illustrated, the tractor screws or propellers 50 are located behind the tail unit 51 so that the air stream entering the propellers is utilized rather than the slip stream flowing back. The principle in either instance is identical. As for the tail skid, in Fig. 3 it will be noted that it too is Toward its rear end the skid is The conven-' curved back and up although to a lesser extent than shown in Fig 1. Again however, the principle of launching is the same as both types of machine can be rocked back sufliciently to nose the end of the machine almost if not quite straight'up in the air.

By slip stream as used in the specification and claims is meant both the entering and exit stream of air passing through the propeller or propellers.

What is claimed is:

1.- In an aeroplane in which the control surfaces lie in the propeller slip stream, a v

landing gear comprising skids having their centers of longitudinal curvature located substantially at the center of gravity of the machine whereby the airplane can be rocked backwardly toward a vertical position under the action of said control surfaces.

2. A landing gear for airplanes compris- I ing skids having their center of longitudinal curvature located substantially at the center of gravity of the machine.

8. In combination, an airplane having its control surfaces bathed by the propeller slip stream together with a rearwardly and up wardly inclined landing gear so situated that the action of the slip stream onthe control surfaces may rock the machine backward to a substantially vertical position.

4:. In an aircraft, the combination of a body, a supporting surface, control surfaces, a propelling power plant including a propeller having an axis of rotation parallel with the longitudinal axis of the body,"the relative arrangement of the propeller to the supporting surface and the control surfaces being such that the slip stream of the former is directed over both the supporting surface and thecontrol surfaces, and a landing gear for the craft extended rearward ly beyond the trailing edge of the supporting surface to support the machine in starting andlanding whether or not the body is substantially horizontal or substantially vertical.

5. In an airplane, a propelling power plant including a propeller, a control surface mounted in the propeller slip stream and distantly removed from the transverse vertical plane of the center of gravity, a

landing gear having a longitudinal curvature in which the. center of the curvature is substantially coincident with the center of gravity, the relation of landing gear to the control surfaces being such that the action of the slip stream on the control surface will rock the machine fore and aft toward a vertical position.

10 gravity constituting a support for the maageae eoa chine in starting and landing with the foody substantially vertical, and that portion of the landing gear extended ahead of the cen:

ter of gravity of the craft constituting a support for the machine in starting and landing with the body substantially hori-- zontal.

-ln testimony whereof I hereunto affix my signature;

- ALBERT ZAHM. 

